EP2039692A1, to Daicel Chemical Industries, LTD of Osaka, Japan, reports (see paragraph [0002]) that 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylate, 1,2,8,9-diepoxylimonene and a compound corresponding to a ∈-caprolactone oligomer, except with 3,4-epoxycyclohexylmethanol and 3,4-epoxycyclohexanecarboxylic acid bonded to both terminals respectively through ester bonding (all being available from Daicel Chemical Industries, Ltd. under the trade names CEL-2021P, CEL-3000 and CEL-2081, respectively) give cured articles through reactions in the presence of various curing agents or curing catalysts where the properties of the resulting epoxy cured articles, thermal stability, transparency, and satisfactory dielectric properties, originate from the alicyclic skeletons of such compounds. However, in paragraph [0003] of the application, problems relating to the deterioration of properties in some applications or low reactivity for curing is noted for such exemplary materials.
At paragraph [0004], EP2039692A1 refers to three references for preparing a 3,4,3′,4′-diepoxybicyclohexyl compound, JP-A No. 2004-99467, JP-A No. 2004-204228 and the Russian document Neftekhimiya, 1972, 12, 353, that each suffer from both insufficient reactivity upon curing and insufficient thermal stability of the cured article prepared therefrom. At paragraph [0007], the application disclosing that after intensive investigations, it was found that each of the aforementioned methods for preparing the 3,4,3′,4′-diepoxybicyclohexyl compound suffered from also providing “not small amounts of isomers differing typically in the position of epoxy groups on the cyclohexane ring”. Further, such paragraph reports that by an alternate process discovered by the inventors they use could the 3,4,3′,4′-diepoxybicyclohexyl compound having a very small content of isomers and that curing of such compound provided “a cured article that has a higher glass transition temperature to thereby have significantly improved properties such as thermal stability” with “a very high curing reaction rate”.
As a result, at paragraph [0008] EP2039692A1 states that “in the present invention, an alicyclic diepoxy compound comprises a 3,4,3′,4′-diepoxybicyclohexyl compound represented by following Formula (1):

where “In the Formula (1), R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16, R17, and R18 are the same as or different from one another and each represent a hydrogen atom, a halogen atom, a hydrocarbon group which may have an oxygen atom or a halogen atom, or a substituted or unsubstituted alkoxy group. The alicyclic diepoxy compound may contain an isomer of the 3,4,3′,4′-diepoxybicyclohexyl compound as an impurity. When the isomer is contained in the alicyclic diepoxy compound, a content of the isomer is less than 20% in terms of peak area ratio based on the total peak areas of the 3,4,3′,4′-diepoxybicyclohexyl compound and the isomer.”
While it is believed that the above stated invention of EP2039692A1 is useful and capable of providing the results and articles described therein, it is noted that the purity of such 3,4,3′,4′-diepoxybicyclohexyl compound, with respect to epoxy isomers, is limited to only “less that 20%” and as provided in the examples provided by the application to a minimum of 9% (see, PREPARATION EXAMPLE 1 at paragraph [0072]). Therefore it is believed that providing methods of making 3,4,3′,4′-diepoxybicyclohexane, as well as other alicyclic diepoxides, that are essentially free of diepoxide isomers of a desired product will be useful.